1. Field of Invention
This invention relates to earthworking scrapers, specifically those that pivot around a vertical axis.
2. Description of Prior Art
Earthworking scrapers are well known in the art. They are designed to be pushed, pulled,
or both pushed and pulled. The implements are either self propelled or propelled by a separate, detachable motive source. There are many various arrangements for the adjustment of the blade position. The prior art is replete with ways to control the depth of the grading tool, including depth guides such as skids, wheels, rollers and the like.
Many grading implements are designed to be connected to utility vehicles by means of a three point hitch. This allows for the disengagement of the tool with the surface of earth, or other material being graded, by raising the implement. This lifting of the grader is necessary to position the implement to grade in a different direction. The disengagement of the grader is time consuming and inefficient.
The three point hitch does not allow the application of any additional downward pressure on the grading tool, in some cases allowing the tool to ride up over a high spot on the surface being graded, and often requiring repeated attempts to shave the material being graded down to the required elevation. U.S. Pat. No. 2,749,631 to Thompson (1956) discloses a three point hitch scraper blade that rotates around a vertical axis. This type of implement, having limited means of depth control, tends to cut too deeply in areas of loosened soil. Constant depth adjustment of such implements, is required to achieve the desired result. The three point hitch is commonly used as a rear hitch on a tractor. The monitoring of the grader attached with a three point hitch mechanism causes the operator of the tractor to twist around to look to the implement and causes operator discomfort and fatigue.
A depth control device, which requires less operator attention to achieve the desired cut and fill results, is commonly used in the art. U.S. Pat. No. 3,234,669 to Kachnik (1966) shows a wheel as an effective depth control device. Wheels or rollers are frequently employed for this purpose. The caster wheel is well known and used in the art as a means of depth control for a scraper blade. This rotateable wheel attachment may also serve as an effective ground support member. The castering motion of the wheel does not change the orientation of the scraper blade resulting in a limited effectiveness of the scraper in sharp turning maneuvers.
Earthworking scrapers, designed to be towed behind a vehicle, are present in the prior art. U.S. Pat. No. 6,112,828 to Leal (2000) shows an implement that has pivotably attached wheels, whose adjustment provides a controllable means of raising or lowering the blade. The simple pivoting on a pin hitch arrangement, commonly used to connect the implement to the tow vehicle, does not allow the implement to be lifted off the ground. Repositioning the implement requires more space to maneuver, and this type of grading implement is more difficult to use in confined spaces, or areas where there are obstacles to maneuver around.
Bi-directional surface leveling implements are more efficient due to their ability to grade in one direction, stop, and reverse direction without repositioning the implement or disengaging the tool from the surface being graded. U.S. Pat. No. 6,168,348 B1 shows a type of implement, when attached to a skidsteer utility vehicle, that has a wider range of possible movement than most grading implements. However, it is still frequently necessary to reposition the implement when grading in confined spaces or when working around obstacles. In the process of turning the skidsteer vehicle the surface being worked is often disturbed and requires additional leveling.
A well developed area of the art employs a blade that pivots around a vertical axis. This gives the implement added capability to move the materials being worked lateral to the direction of the draft more effectively. These implements, however, do not provide an effective means for moving the implement as a whole in a lateral direction.
Multiple blades for moving earth laterally to the direction of the draft of the implement exist in the prior art U.S. Pat. No. 6,283,225 B1 to Hermonson (2001) shows an implement attached to a skidsteer utility vehicle capable of such action. To reposition such an implement of this type the turning action of the skidsteer disturbs the surface being worked and necessitates another pass with the implement to grade the surface again. An implement of this type does not have the ability to adjust the height of the blades effectively. The earthworking scrapers available today suffer from a number of disadvantages:                (a) Grading implements currently available require a disengagement from the surface being worked to reposition the implement for a change of direction.        (b) The skidsteer utility vehicles commonly used for a motive source cause a disturbance of the surface being worked as a result of their mode of turning in a short radius.        (c) Most graders have no ability to move soil in one direction, stop and without disengaging from the surface being worked, move the soil in any other desired direction.        (d) Poor visibility of the scraper blade is a common problem.        (e) Many of the graders in use today have a limited range of depth control adjustment.        (f) An inability to apply downward pressure while turning sharply is a disadvantage of the currently available implements.        (g) A limited adaptability to different soil conditions necessitates waiting for the ideal conditions before attempting to perform the earthworking task.        (h) Most of the currently available graders have objects extending beyond the lateral edges of the scraper that can damage trees, houses, and other valuable objects at the work site as the grader is being used.        (i) A grader that is connected to a motive source that has the ability to rotate a lift arm assembly around a vertical axis is unavailable in the market place today.        (j) A hydraulic excavator is not well suited to grading.        (k) A pivotable grader of the existing art has no easily interchangeable pivotable component.        (l) An interchangeable pivotable component is unavailable in the marketplace.        